Grandpa Raptor? Find Brings Science Closer To First Dinosaur

A team of scientists working in Argentina has found the closest thing yet to the granddaddy of all dinosaurs, an artful dodger about the size of a small dog that sprinted after prey on its hind legs.

The creature, named "Eoraptor" by its discoverers, appeared only 1 million or 2 million years after the first dinosaur evolved from a line of ancient reptiles. "We're just a few steps away from the common ancestor," Paul Sereno, a University of Chicago paleontologist, said at a news conference yesterday. "Eoraptor may be the closest we ever come."

Sereno, who led the joint U.S. and Argentine expedition that found the fossil, said the discovery supports theories that the earliest dinosaurs were small, carnivorous animals that walked on two legs. Geological evidence suggests that the fossil is between 225 million and 230 million years old.

It is one of the two earliest dinosaurs found. The other, which existed about the same time, was the meat-eating, 15-foot-long Herrerasaurus, also found in Argentina. But Sereno said the Eoraptor is clearly a more primitive style of animal.

Sereno, 35, told reporters that the Eoraptor had the teeth and claws of a carnivore, making it an ancestor to a group of meat-eating dinosaurs called theropods, which included the towering Tyrannosaurus Rex.

But the ancient creature lacked the flexible jaws and broad pelvic bones of its descendants.

David Weishampel, a paleontologist who teaches at the Johns Hopkins School of Medicine, said the fossil would help scientists understand the rapid increase in the number of dinosaur species after their first appearance.

"We know very little about the first ones, the most primitive forms," he said. "It's always a good idea to have a good idea about who's there at the very beginning, because they'll tell us a lot about the historical pathways followed by the descendants."